In the prior art, a variety of studies were made to tailor the formulation of golf ball-forming material for the purpose of endowing golf balls with better rebound. Golf balls are required to have not only good rebound, but also a diversity of properties including a soft feel when hit and durability. It is a key to find a higher order compromise among these properties.
For example, JP-A 2002-253703 discloses a technique of incorporating a fullerene or derivative thereof in a rubber material (typically polybutadiene rubber containing at least 40% of cis-1,4-bond) of which a golf ball core is made, thus providing a golf ball having excellent rebound performance and a pleasant feel when hit. Because of its special molecular configuration, the fullerene or derivative thereof is often difficult to uniformly and finely disperse in a medium as compared with commonly used additives. If an additive is not uniformly and finely dispersed in a golf ball-forming material, the golf ball made therefrom may be adversely affected, typically detracting from durability to consecutive shots.
There is a need for an effective means of finely dispersing a fullerene or derivative thereof in a golf ball-forming material.